docs: def set_idle_priority(pid=None):
      """
      Puts a process in the idle io priority class.
  
      If pid is omitted, applies to the current process.
      """
  
      if pid is None:
          pid = os.getpid()
      lib.ioprio_set(
          lib.IOPRIO_WHO_PROCESS, pid,
          lib.IOPRIO_PRIO_VALUE(lib.IOPRIO_CLASS_IDLE, 0))